2013 - May R3 Journal Review

Maekawa, K et al. Extracorporeal Cardiopulmonary Resuscitation for Patients With Out-of-Hospital Cardiac Arrest of Cardiac Origin: A Propensity-Matched Study and Predictor Analysis. Crit Care Med.May 2013;41(5):1186–1196 . Extracorporeal cardiopulmonary oxygenation (ECMO) and extracorporeal cardiopulmonary resuscitation (ECPR) is a class 2b recommendation for reversible cardiac arrest and has already been a standard of care in Japan. Encouraging results of ECPR for patients with refractory cardiac arrest have been shown. However, the independent impact on the neurologic outcome remains unknown in the out-of-hospital population. The authors of this paper sought to estimate survival of cardiac arrest with good neurologic outcome and investigate potential clinical variables that could predict neurologic outcomes following ECPR and conventional cardiopulmonary resuscitation (CCPR).

A post hoc analysis of data from a prospective observational cohort was performed at a tertiary care university hospital in Sapporo, Japan (January 2000 to September 2004). A total of 162 (out of 398) adult patients (age 16 years or older) with witnessed cardiac arrest of cardiac origin (excluding origins such as trauma, OD, drowning, etc.) who had undergone CPR for longer than 20 minutes (53 in the ECPR group and 109 in the conventional CPR group) were included. ECPR was determined by attending physicians (based on clinical judgment) and ECMO was implanted by designated ECMO teams. Post resuscitation care was at the discretion of the attending physicians.

The primary endpoint was neurologically intact survival at three months after cardiac arrest. Propensity score matching (using a nonparsimonious logistic regression model) was used to reduce selection bias and balance characteristics and variables that could affect outcome; from this, 24 patients from each group were selected. Intact survival rate was higher in the matched ECPR group than in the conventional CPR group (29.2% [7/24] vs. 8.3% [2/24], log-rank p = 0.018), with a number needed to treat of 4.8 to achieve one favorable outcome. According to the predictor analysis, pupil diameter emerged as the most powerful independent predictor of neurologic outcome (adjusted hazard ratio, 1.39 per 1-mm increase; 95% confidence interval, 1.09–1.78; p = 0.008). In univariate analysis, the following pre-ECPR variables were associated with unfavorable neurologic outcomes: pre-existing arrhythmia including treated and untreated ones, atropine administration, CPR duration, pupil diameter (>6mm) on hospital arrival, shockable rhythm on hospital arrival, spontaneous breathing on hospital arrival, and serum lactate levels.

The authors of this paper conclude that ECPR can improve neurologic outcome after out-of-hospital cardiac arrest of cardiac origin and they conclude that a pupil diameter (<6mm) on hospital arrival may be a key predictor to identify ECPR candidates. Limitations to this study include: only patients with witnessed arrest in an out-of-hospital population were included, ECPR was initiated not by randomization but on the basis of the attending physicians’ decision, the power of the study is limited based on sample sizes and difference between CCPR and ECPR, subsequent interventions after ECPR were not included in the predictor analyses, the quality of CPR and the defibrillation time interval were not controlled between comparison groups because of their nature and lastly, the impact of ECPR may be attributed, to some extent, to observer bias rather than extracorporeal support.

- Crum

Dart RC, et el. A Randomized, Double-Blind, Placebo-Controlled Trial of a Highly Purified Equine F(ab)2 Antibody Black Widow Spider Antivenom. Ann Emerg Med. April 2013; 61(4):458-467. This is a multi-center, randomized, double-blind, placebo-controlled trial testing the use of a novel F(ab)2 antivenom in patients with moderate to severe pain caused by black widow envenomation. The study included patients at least 10 years of age who presented within 72 hours of symptom onset of presumed black widow spider bite and were given a clinical diagnosis of lactrodectism by two independent clinicians. They had to present with a visual analog scale pain score of at least 40mm to receive either placebo or antivenom. A total of 26 patient were included in study; 13 to antivenom and 11 to placebo. 1 patient was excluded for + UPT and 1 for failing to reach severity on pain scale. The results showed that the antivenom group had a quicker time to improvement in pain score; however this was only significant at the 1 hour mark. It did not show that antivenom produced a greater overall pain reduction. There were no deaths or serious adverse events. The limitations of this study include small sample size, many treatment failures, and protocol deviations. Also, one patient may have accidentally gotten the wrong treatment arm. This study also does not include cost-benefit analysis, which might be useful considering the new drug may be expensive and black widow bites are not deadly. Overall, this novel antivenom needs further investigation.

- Clamp

Sun BC, et al. Effect of Emergency Department Crowding on Outcomes of Admitted Patients. Ann Emerg Med. June 2013; 6111(6): 605-611. This study is a multi-center retrospective cohort study of adult admissions to California non-federal hospitals to attempt to assess if there is a difference in patient outcome during times of ED crowding. The study looked at almost 1,000,000 admissions during 2007 to California hospitals of adult patients (>18), and then broke them down into admissions when hospitals were on diversion, and when they were not on ambulance diversion, as a surrogate marker for ED crowding. It was found that patients admitted to a hospital that was on ambulance diversion had 5% greater odds of inpatient death, 0.8% longer length of stay, and 1% greater cost of stay. All of these were found to be statistically significant. Although ambulance diversion seems to be a fairly poor indicator of true ED overcrowding given that many busy hospitals, UCD for instance, have a no diversion policy, the overall message of the article is that crowding is bad for patients on many levels, and ED boarding needs to be addressed.